Effect of Oral Rehydration Solution on Fatigue during Outdoor Work in a Hot Environment: A Randomized Crossover Study

Abstract

The effects of an oral rehydration solution (ORS) on fatigue were studied in workers engaged in manual work during the summer. One hundred and fifty-three workers engaged in loading cargo onto aircraft at Tokyo International Airport who consented to participate in the study were the subjects. The study was carried out on two summer days with fine weather during the daytime shift. The subjects were randomly divided into two groups: with one group restricted to ORS intake and the other group having free-choice of their favorite drink (FAD) in a randomized crossover study. The subjects were asked about the amount of beverage that they consumed and the type of FAD that they chose on the days of the survey. The effects of the ORS and the FAD were compared using a visual analogue scale (VAS) to determine the degree of fatigue experienced immediately after completing work. The average wet bulb globe temperature (WBGT) on the survey days was 30 degrees C. The beverage intake during work was 1,000 ml for most participants and the most commonly chosen types of FAD were tea and coffee. The fatigue VAS was significantly lower on the ORS intake days than on the FAD intake days (50.0 +/- 18.3 vs. 53.9 +/- 16.3). The results of this study suggest that the intake of ORS during outdoor work in a hot environment would be effective for preventing industrial accidents and heat stroke. It is important to select an appropriate drink to ensure adequate intake of water and electrolytes.